1. Field of the Invention
The present invention is related to the use of bioreactors for holding media and promoting the growth of biological materials, and in particular transparent bioreactors for growing biological materials requiring a light source, such as aquatic plants.
2. Description of Related Art
Photo-bioreactors are devices that allow photosynthetic microorganisms to grow in a controlled manner. U.S. Pat. No. 5,846,816 to Forth (“Forth”) discloses a biomass production apparatus including a transparent chamber 10 which has an inverted, triangular cross-section, as is shown in FIG. 1 of Forth. Extending through the chamber is a first conduit 22 which has a plurality of perforations along its length to allow the introduction of gasses into the chamber. Also extending through the chamber are a pair of heat exchange conduits 26 connected to a supply of heat exchange medium.
The passage of air entering through the conduit establishes a distinctive flow pattern that causes the liquid in the chamber to circulate up through a central region of the chamber, across the upper portion of the chamber below a cover 16, and down along the chamber sidewalls 20 back to the conduit, as is shown in FIG. 3 of Forth. The cover includes two vents 28 through which the circulating gases exit the chamber. Ostensibly the passage of air and circulation of the liquid ensures that the biological matter suspended therein is exposed to light and also prevents the biological matter, such as algae, from adhering to the walls of the chamber.
Although the bioreactor disclosed by Forth promotes the growth of biological matter, it is generally not useful for applications requiring a sterile growth environment. The vents are open to external air which may include airborne contaminants. Such contaminants are especially troublesome for pharmacological applications wherein strict Food and Drug Administration guidelines for avoiding contamination must be met.
In addition, the constant circulation of the liquid required by Forth interferes with the growth of some types of biological matter. For instance, fully differentiated aquatic plants from the lemnaceae or “duckweed” family are fresh-water plants that grow best on the surface of the water. Such surface growing plants typically prefer relatively still water to support and promote optimal growth.
Therefore, it would be advantageous to have a photo-bioreactor system for promoting the growth of plant biological materials in a relatively sterile environment isolated from contaminants. It would be further advantageous if the system were capable of promoting growth of surface growing aquatic plants, such as the duckweed family of plants.